1. Field of the Invention
The present invention relates to a digital signal recording apparatus and, more particularity, to a digital signal recording apparatus for recording digital audio and video signals.
2. Description of the Prior Art
Consumer-use digital video Cassette Recorders (VCR) for recording audio and video signals as digital signals are now commercially available. The consumer-use digital Video Cassette Recorder (VCR) market, however, has been constrained by the various methods applying video compression (band width compression) technologies to the video signal that have been proposed as a means for reducing cassette size.
In FIG. 5A, an example of the on-tape positioning of the video signals and audio signals recorded by a digital VCR is shown. The audio and video signals for one frame are recorded to ten tracks Tr0 to Tr9 on tape. It is to be noted that the audio and video signals are recorded to specific and different segments Sa and Sv of each track.
As shown in FIG. 5B, each track Tr further comprises a plurality of recording blocks Br (FIG. 6) in the audio and video signal segments Sa and Sv. Each audio signal segment Sa is comprised of a predetermined number of audio data recording blocks Ba and parity recording blocks Bp. Similarly, each video segment Sa is comprised of a predetermined number of video data recording blocks Bv and parity recording blocks Bp.
The audio data recording block Ba, the video data recording block by, and the parity recording block Bp has principally the same construction of the recording block Br, as best shown in FIG. 6. The audio or video signals are divided into a plurality of small data blocks Db which is recorded in one recording block Br. Each data block Db is complemented by a synchronization signal Ds for bit synchronization, ID information indicating the location of the recording data block in the frame, and parity data Dp for error correction. In parity recording blocks Bp, only parity data is recorded in its data Db instead of video or audio signal data.
When the data blocks Db in the recording blocks Br are subsequently reproduced, those complementing information makes it possible to reproduce the original video signal and/or audio signal from the recorded data block Db in the recording blocks Br.
Because distortion caused by video compression processing increases when video compression and expansion are repeated, it is preferable when copying between VCR units to copy the data in the video compressed state. This means that it is preferable to copy the data as in the form of recorded data block Db in the recording block Br units.
It is not guaranteed, however, that all recorded data in recording blocks in each frame can be reproduced because of variable speed reproduction, transmission errors, and other factors relating to VCR operation. When the recorded data blocks in any recording block units for one frame cannot be reproduced, the recording block unit(s) from other frame(s) are substituted for the recording block units whose recorded data block could not be reproduced, so that the unreproducible recorded data block(s) are reproduced by simulation.
When substitution by recording block unit is used in this way, however, recording block units from plural frames will be mixed into one frame (in the ten tracks shown in FIG. 5) on the copy tape. The audio signal, however, cannot be reproduced if the time-base relationship of the sequential recording block units is not maintained. Only the information for adjacent frames can be obtained with the ID information associated with each recording block units in this conventional digital VCR, however, and it is not possible to differentiate plural frames. In addition, frame information is lost during reproduction because of the substitution of ID information during recording when copying. It is therefore difficult to determine the time-base relationship of each recording block.
As a result, it is difficult to reproduce the audio signal when variable speed reproduction of recorded data blocks or error correction is applied to the recording block units in the conventional digital VCR.